Pump with rotor having arcuate slots and vanes

ABSTRACT

A pump includes a shaft to rotate about a longitudinal axis, a rotor, at least two arcuate slots extending continuously into and through the rotor, wherein each of the slots is curved along a longitudinal slot axis, and at least two arcuate vanes, each of the vanes being shaped to be slidably seated in one of the slots, each of the vanes being movable in the corresponding slot between an extended position with the external edge of the vane adjacent the interior sidewall of the housing, and a retracted position wherein the external edge of the vane does not extend beyond the cylindrical surface of the rotor. Each of the vanes is spaced from an adjacent vane about the rotor such that there is always at least one vane positioned between the fluid inlet and fluid outlet ports.

TECHNICAL FIELD

The embodiments disclosed herein relate to apparatus for driving fluids, and particular to such apparatus having one or more arcuate vanes for pumping or compressing fluid.

INTRODUCTION

Compressors and pumps are commonly used to transfer mechanical energy to fluids. Some of these compressors and pumps have rotary designs, which can provide efficient and continuous energy transfer.

Example devices are is described in U.S. Pat. No. 7,597,548 entitled “Dual Arc Vane Pump” issued Oct. 6, 2009, U.S. Pat. No. 6,945,218, entitled “Rotary Pistons” issued Sep. 20, 2005, and U.S. Pat. No. 6,554,596 entitled “Fluid Turbine Device” issued Apr. 29, 2003, to common inventors.

These patents relate to rotary pistons, motors and pumps having encased rotors with radially extending vanes which move in and out of the rotors, depending on their location within the casing. The vane movement in and out of the rotor is at least partly achieved by cam surfaces within the casing. The walls of the casing are not of uniform radius, and are formed so as to facilitate movement of the vanes and flow of fluid between inlet and outlet ports in the casing. These pumps work well but there is a need from an improved pump.

SUMMARY

According to some embodiments, there is a rotary pump including a shaft to rotate about a longitudinal axis; a rotor centrally secured to the shaft, the rotor having a body with spaced ends and a cylindrical surface extending between the spaced ends; a rotor disk secured to each end of the rotor and secured at a centre of the rotor disk to the shaft; a housing encasing the shaft, the rotor disks, and the rotor within an internal cavity, the housing having interior end walls and an interior sidewall, with fluid inlet and fluid outlet ports in the interior sidewall, a first section of the interior sidewall of the housing being cylindrical and curved with a constant radius over an angle of about approximately 180°, the first section being spaced a constant distance from confronting sections of the cylindrical surface of the rotor, and a second section of the interior sidewall of the housing extending between the extremities of the first section of the interior sidewall, the cylindrical surface of the rotor being proximal to the interior sidewall of the housing between the fluid inlet and fluid outlet ports about midway along the second section, the fluid inlet and fluid outlet ports being located in the second section of the interior sidewall of the housing; at least two arcuate slots extending continuously into and through the rotor, wherein each of the slots is curved along a longitudinal slot axis; and at least two arcuate vanes, each of the vanes being shaped to be slidably seated in one of the slots, each of the vanes being movable in the corresponding slot between an extended position with the external edge of the vane adjacent the interior sidewall of the housing, and a retracted position wherein the external edge of the vane does not extend beyond the cylindrical surface of the rotor, each of the vanes being spaced from an adjacent vane about the rotor such that there is always at least one vane positioned between the fluid inlet and fluid outlet ports; wherein each of the vanes includes shoulder portions extending beyond the ends of the rotor; wherein the rotor disks include grooves aligned with the rotor slots and being configured for slidably receiving the shoulder portions of the vanes; and wherein low pressure of the fluid at the fluid inlet port assists each of the vanes to retract and high pressure of the fluid at the fluid outlet port assists each of the vanes to extend.

Each of the vanes may include an arcuate body portion conforming to the shape of the slot and a tip portion extending from the arcuate body portion.

The tip portion may be hingedly attached to the arcuate body portion to ride on the interior sidewall of the housing.

The body of the rotor may include peripheral cutout portions shaped to receive the tip portions of the vanes when the vanes are in the retracted position.

The tip portions may include magnetic components and the rotor body includes magnetic components of similar polarity to repel the tip portion from the rotor body.

The magnetic components of the rotor may be located in the peripheral cutout portion.

The tip portion may have a triangular profile.

The arcuate body portion may include an external hinge and the tip portion may include an arcuate surface and a flat surface.

The tip portion may include magnetic components and the arcuate body portion may include magnetic components of similar polarity to repel the tip portion from the arcuate body portion.

The rotary pump may further include a shock absorber placed in the grooves to prevent the vanes from impacting the ends of the grooves during the retraction of the vanes.

The second section of the interior surface may include an outlet section that causes the vane to retract.

The arcuate slots may be diametrically opposed such that a distal vane end of the first arcuate slot is opposite on the rotor to a distal vane end of the second arcuate slot.

The arcuate slots may not pass through the centre of axis of rotation of the rotor.

The shaft may be rotated by an external drive shaft.

The rotor disk may include a gear that meshes with a drive gear on the external drive shaft.

The housing and the vanes may be constructed so that, during operation of the rotary piston, fluid entering the housing through the inlet port is carried by the rotor, in each of compartments formed between adjacent vanes, the rotor surface between the vanes and the corresponding sections of the end walls and interior sidewall of the housing, until the adjacent vanes encompass the outlet port whereby the fluid is allowed to leave the housing.

According to some embodiments, there is a rotary pump including a shaft to rotate about a longitudinal axis; a rotor centrally secured to the shaft, the rotor having a body with spaced ends and a cylindrical surface extending between the spaced ends; a housing encasing the shaft and the rotor within an internal cavity, the housing having interior end walls and an interior sidewall, with fluid inlet and fluid outlet ports in the interior sidewall, a first section of the interior sidewall of the housing being cylindrical and curved with a constant radius over an angle of about approximately 180°, the first section being spaced a constant distance from confronting sections of the cylindrical surface of the rotor, and a second section of the interior sidewall of the housing extending between the extremities of the first section of the interior sidewall, the cylindrical surface of the rotor being proximal to the interior sidewall of the housing between the fluid inlet and fluid outlet ports about midway along the second section, the fluid inlet and fluid outlet ports being located in the second section of the interior sidewall of the housing; at least two arcuate slots extending continuously into and through the rotor, wherein each of the slots is curved along a longitudinal slot axis; and at least two arcuate vanes, each of the vanes being shaped to be slidably seated in one of the slots, each of the vanes being movable in the corresponding slot between an extended position with the external edge of the vane adjacent the interior sidewall of the housing, and a retracted position wherein the external edge of the vane does not extend beyond the cylindrical surface of the rotor, each of the vanes being spaced from an adjacent vane about the rotor such that there is always at least one vane positioned between the fluid inlet and fluid outlet ports; wherein low pressure of the fluid at the fluid inlet port assists each of the vanes to retract and high pressure of the fluid at the fluid outlet port assists each of the vanes to extend.

According to some embodiments, there is a rotor for a pump. The rotor includes a rotor body with spaced ends and a rotor surface extending between the spaced ends, an arcuate slot extending continuously into and through the rotor body, wherein the slot is curved along a longitudinal slot axis, and an arcuate vane being shaped to be slidably seated in the slot, the vane being movable in the slot between an extended position with an external edge of the vane adjacent the interior sidewall of a housing, and a retracted position wherein the external edge of the vane does not extend beyond the rotor surface of the rotor body.

The rotor body may include two arcuate slots and the rotor may include two arcuate vanes.

The arcuate slot may be curved along a longitudinal slot axis that is parallel with a rotator rotation axis of the rotor.

The vane may be fluidly sealed in the arcuate slot such that fluid is inhibited from passing through or around the vane in the arcuate slot.

The arcuate vane may include an arcuate body portion conforming to the shape of the slot and a tip portion extending from the arcuate body portion.

Other aspects and features will become apparent, to those ordinarily skilled in the art, upon review of the following description of some exemplary embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings included herewith are for illustrating various examples of articles, methods, and apparatuses of the present specification. In the drawings:

FIG. 1 is an exploded view of an apparatus for driving fluid, in accordance with an embodiment;

FIGS. 2A to 2D are perspective, end, side, and section views, respectively, of the apparatus of FIG. 1;

FIGS. 3A and 3B are end and perspective views, respectively, of a rotor of the apparatus of FIG. 1;

FIG. 4 is a perspective view of a vane of the rotor of FIGS. 3A and 3B;

FIGS. 5A and 5B are end and perspective views, respectively, of a rotor having a magnetic vane, in accordance with an embodiment;

FIGS. 6A and 6B are side and sectional views, respectively, of the rotor of FIGS. 5A and 5B;

FIGS. 7A to 7D are end, perspective, side, and sectional views, respectively, of the magnetic vane of FIGS. 5A and 5B;

FIGS. 8A to 8D are end, perspective, side, and sectional views, respectively, of a vane, in accordance with a further embodiment;

FIGS. 9A and 9B are end and perspective views, respectively, of the arcuate body portion of the vane of FIGS. 8A to 8D;

FIGS. 10A and 10B are end and perspective views, respectively, of the tip portion of the vane of FIGS. 8A to 8D; and

FIGS. 11A to 11H are sectional views of the apparatus of FIG. 1 cycling through a fluid driving cycle.

DETAILED DESCRIPTION

Various apparatuses or processes will be described below to provide an example of each claimed embodiment. No embodiment described below limits any claimed embodiment and any claimed embodiment may cover processes or apparatuses that differ from those described below. The claimed embodiments are not limited to apparatuses or processes having all of the features of any one apparatus or process described below or to features common to multiple or all of the apparatuses described below.

Referring to FIGS. 1 through 3B, illustrated therein is an apparatus 100 for use in driving fluid. The apparatus 100 may be a rotary piston device that compresses or pumps fluids such as a pump. The apparatus 100 includes a housing 102 having an interior chamber 104 enclosed by two rotor disks 105 and two end walls 106. The interior chamber 104 is in communication with a fluid inlet port 120 for receiving the fluid and a fluid outlet port 122 for expelling the fluid.

A central shaft 126 extends through the housing 102, rotating about a longitudinal rotor axis A (FIG. 2C). A rotor 108 is centrally secured to the central shaft 126. The rotor 108 has a body with a rotor surface 127 extending between spaced rotor ends 129. The rotor surface may be cylindrical. Secured to rotor ends 129 are rotor disks 105 centrally mounted on the central shaft 126.

The rotor disks 105 have a circumferential gear 128 that meshes with a secondary circumferential gear 125 mounded on a drive shaft 121. The drive shaft 121 can be used to drive rotation of the apparatus 100. The central shaft 126 is mounted through the end walls 106 and rotates on bearings 170, 172. The drive shaft 121 is mounted through the housing 102 and the end walls 106 and rotates on bearings 174, 176.

Turning now to FIG. 2D, the housing 102 is provided with an interior chamber 104 bounded by interior surface 131 of rotor disks 105 and interior side wall 134 extending between those interior surfaces 131. A first section 133 of interior side wall 134 is curved with constant radius over an angle of about 180°, this first section 133 being spaced a constant distance D from confronting sections of rotor surface 127 of the rotor 108.

The interior side wall 134 has a second section 135 extending between the extremities of first section 133. The second section 135 has an inlet section 136 and an outlet section 137 of a generally smaller radius than that of the first section 133. The outlet section 137 causes a vane 110 to retract. The second section 135 has a flat section 138 that extends between the inlet and outlet sections 136, 137. The rotor surface 127 is proximal to the interior side wall 134 of housing 102 at a central section 139 in the flat section 138 and between the fluid inlet port 120 and fluid outlet port 122, which are located in this second section 135 of interior side wall 134. The central section 139 may have a cutout curved to conform with rotor surface 127 of the rotor 108 to provide a fluid seal.

A pair of arcuate slots 115 a, 115 b are provided in rotor surface 127. The arcuate slots 115 a, 115 b may be located at diametrically opposed locations. Each arcuate slot 115 a, 115 b is curved and extends continuously into the rotor 108 to one side of, and through the rotor 108. The slots 115 are curved along a longitudinal slot axis B (shown extending into the figure at FIG. 3A). The longitudinal slot axis B is parallel with the rotator axis A. The curvature of the arcuate slots 115 a, 115 b is opposite to that of the rotor surface 127. For example, the rotor surface 127 is generally circular when sectioned, while the arcuate slots 115 a, 115 b are generally semi-circular and have a center of radius that is not between the centre of the rotor 108 and the arcuate slots 115 a, 115 b. More particularly the center of radius of the arcuate slots 115 a, 115 b is located outside of the rotor 108. Further, the curvatures of the arcuate slots 115 a, 115 b are opposite to each other in that slot 115 a curves in one direction and slot 115 b curves in an opposite direction.

A pair of similarly arcuate shaped vanes 110, 112 are configured to be slidably seated in each arcuate slot 115 a, 115 b of the rotor 108. The vanes 110, 112 are fluidly sealed in the arcuate slots 115 a, 115 b such that fluid can not pass through or around the vanes 110 in the arcuate slot 115 a.

The arcuate slots 115 a, 115 b each include a distal vane end where the vane 110 exits the arcuate slot 115 and a proximal vane end where the vane 110 abuts, when retracted.

The arcuate slots 115 a, 115 b may be diametrically opposed such that the distal vane end of the first arcuate slot 115 a is opposite on the rotor 108 to the distal vane end of the second arcuate slot 115 b. Similarly the proximal vane end of the first arcuate slot 115 a is opposite on the rotor 108 to the proximal vane end of the second arcuate slot 115 b. The arcuate slots 115 a, 115 b do not pass through the centre of axis of rotation of the rotor 108.

The arcuate slots 115 a, 115 b are able to fully house the arcuate vanes 110, 112. In some cases, the arcuate vanes 110, 112, are the same size as the arcuate slots 115 a, 115 b.

The location of the distal vane end and the proximal vane end is determined by the location of the inlet port 120 and the outlet port 122. The distal vane end is positioned away from the proximal vane end and the distal vane end of the first slot 115 a is positioned away from the proximal vane end of the second arcuate slot 115 b dependent on the vane stroke length, rotor size, cam size, and the timing of the cycle. The distal vane end of the first arcuate slot 115 a is 180 degrees away from the distal vane end of the second arcuate slot 115 b.

FIG. 3A illustrates the vanes 112 in an extended position projecting up from rotor surface 127, and the vane 110 in a retracted position within the arcuate slot 115. The radius of the arcuate vane 110 is determined by the length of the vane's extension as well as positioning the arcuate slot 115 during rotation to allow the open end of the rotor slot to vent fluid into the low pressure side of the pump before the arcuate vane 110 begins to retract. The arcuate vanes 110, 112 have a radius greater than the radius of the rotor 108.

If vanes 110 and 112 had a larger radius than shown in FIGS. 2D and 11A-H the vane slot 115 b would vent into the low pressure side of the pump allowing vane 112 to retract before vane 110 is contacting section 133 of the case allowing fluid to pass freely between inlet and outlet ports 120 and 122.

If vanes 110 and 112 had a smaller radius then shown in FIGS. 2D and 11A-H vane 112 would begin to be forced in by section 137 before vane slot 115 b is allowed to vent into the low pressure side and vane 112 would lock into position and therefore the rotor 108 would not be able to rotate any further.

As can be seen in FIG. 2D, the lower vane 110, being in extended position, is in contact with the first section 133 of the interior side wall 134. The other vane 112 however, at this point in rotor travel is in a retracted position filling the arcuate slot 115 b wherein the external edge of the vane does not extend beyond the cylindrical surface of the rotor. When the vanes are in the retracted position, the vanes 110, 112 provide a continuum to rotor surface 127. Fluid inlet and outlet ports 120 and 122 respectively are positioned so that there is always a vane 110 located between these ports.

As can be seen at FIGS. 3B and 4, the vanes 110, 112 have an arcuate section 140 with shoulder portions 123 at each side. The shoulder portions 123 are slidably seated in corresponding grooves 124 in the rotor disks 105. Grooves 124 and shoulder portions 123 support the vanes 110 and limit the extent of travel as the vanes 110 move between a retracted position and an extended position.

In some cases, a shock absorber 150 (shown in FIG. 3A) can be placed in the grooves 224 to prevent the vanes 110 from impacting the ends of the grooves 224 during the retraction of the vanes 110. The shock absorber 150 may be made of a flexible material. The shock absorber 150 is placed at the end of the grooves proximal to the retracted slots 115.

FIGS. 5A to 7D illustrates a rotor assembly 218, in accordance with a further embodiment. The rotor assembly 218 has vanes 210, 212 that include an arcuate body portion 240 and a tip portion 213 extending from the arcuate body portion 240. The arcuate body portion 240 rides on the interior surface of the housing. The tip portion 213 is attached to the arcuate body portion 240 at hinge 244. The arcuate body portion 240 and the tip portion 213 are shaped so that when the vane 210 is in the retracted position the vane 210 sits in a peripheral cutout portion 246 extending longitudinally along the rotor surface 227. The arcuate body portion 240 conforms to arcuate slots 215 of the rotor 208. The tip portion 213 of each vane pivots at hinge 244, so that the tip portion 213 is seated in and fills its peripheral cutout portion 246 when the vane 210 is in the retracted position. The tip portion 213 extends between the shoulder portions 223, which ride in the arcuate slots 215 of the rotor 205.

The tip portion 213 may be a foil that will tip out from the rotor 218 to help the vane 210 cut through the fluid being driven by the pump 200. The tip portion 213 may reduce drag on the vane 210 as the vane 210 extends. In some embodiments, the tip portion 213 is a replaceable wear point.

The tip portion 213 includes magnetic components 242 and the rotor 208 includes magnetic components 243 of similar polarity to repel the tip portion 213 from the rotor 208. The magnetic components 243 of the rotor 208 are located in the peripheral cutout portion.

Turning now to FIGS. 8A-10B, a vane 310 includes a tip portion 313 having a triangular profile, in accordance with a further embodiment. The vane 310 includes an external hinge 344 attached to an arcuate body portion 340 that receives the tip portion 313. The tip portion 313 has an arcuate surface 346 and a flat surface 446. The flat surface 446 includes the magnetic elements 342.

In some cases the vane is made as a one piece composite with the arcuate body portion being made from a rigid material and the tip portion being made from a flexible material such as rubber or silicone.

Turning now to FIGS. 11A-11H, during operation of the apparatus 100, the vanes 110, 112 and the interior side wall 134 are configured so that the vanes 110, 112 are biased toward the extended position by pressure and through centrifugal force as rotor 108 spins. The vanes 110, 112 are moved towards the retracted position under urging of the interior side wall 134. The bias generated on the vanes 110, 112 is overcome and the vanes 110, 112 are moved from the extended to the retracted position through the cam effect of second section 135 of interior side wall 134 acting on vanes 110, 112.

During operation of apparatus 100, fluid entering the housing through fluid inlet port 120 is carried in the corresponding one of two compartments 104 a (low pressure), 104 b (high pressure) between vanes 110, 112 as rotor 108 rotates. The rotor 108 rotates in Direction B and compartment 104 b passes the fluid outlet port 122, where fluid is expelled from the low pressure compartment 104 b and the housing 102, as the volume of the low pressure compartment 104 b is collapsed. The compartment 104 a is low pressure at the fluid inlet port 120, and high pressure at the fluid outlet port 122.

FIG. 11B indicates the beginning of the cycle for vane 110, and the end of the cycle for vane 112. The fluid in compartment 104 b is being expelled by the vane 112 at fluid outlet port 122, while the fluid in compartment 104 a is being pushed by vane 110.

At FIG. 11C, the arcuate slot 115 b passes by the central section 139 and passes from the high pressure compartment 104 b to the low pressure compartment 104 a (at FIG. 11D) as the vane 112 rotates into the second section 135. At the same point in the cycle, the low pressure compartment 104 a becomes the high pressure compartment 104 b (FIG. 11D) as the vane 110 rotates into the first section 133. The high pressure 104 b that enters the arcuate slot 115 a assists the vane 110 to extend. The vane 112 retracts from the low pressure 104 a that enters the arcuate slot 115 b. FIG. 11D shows the vane 112 beginning to retract into arcuate slot 115 b.

At FIG. 11E, the vane 112 is fully retracted into the arcuate slot 115 b. At FIG. 11F, the vane 112 passes the central section 139. At FIG. 11G, the vane 112 has passed the central section 139 and has entered the inlet section 136. At FIG. 11H, the vane 112 is extended by the magnetic elements and the centrifugal forces. The cycle begins again at 11A.

This construction of apparatus 100, by enabling the vanes 110, 112 to pass beyond the rotor centre when in retracted position, may permit the use of smaller diameter rotors in conjunctions with relatively larger vanes. The slot 115 not only extend into the rotor 108 beyond its centre, but also overlap each other, optimizing the use of the space within the small diameter rotor. As well, the strong vane design may enable the pump to operate with just two vanes, while pressures within the compartments are contained at all times by these two vanes.

While the pump is well suited for movement of liquids, it is also suitable for movement of air and hence may serve as a compressor or a vacuum pump. The apparatus 100 may be used in an engine, an air compressor, a vacuum pump, or the like. The fluid being driven by the apparatus 100 may be a liquid and/or a gas.

While the above description provides examples of one or more apparatus, methods, or systems, it will be appreciated that other apparatus, methods, or systems may be within the scope of the claims as interpreted by one of skill in the art. 

1. A rotary pump comprising: a shaft to rotate about a longitudinal axis; a rotor centrally secured to the shaft, the rotor having a body with spaced ends and a cylindrical surface extending between the spaced ends; a rotor disk secured to each end of the rotor and secured at a centre of the rotor disk to the shaft; a housing encasing the shaft, the rotor disks, and the rotor within an internal cavity, the housing having interior end walls and an interior sidewall, with fluid inlet and fluid outlet ports in the interior sidewall, a first section of the interior sidewall of the housing being cylindrical and curved with a constant radius over an angle of about approximately 180°, the first section being spaced a constant distance from confronting sections of the cylindrical surface of the rotor, and a second section of the interior sidewall of the housing extending between the extremities of the first section of the interior sidewall, the cylindrical surface of the rotor being proximal to the interior sidewall of the housing between the fluid inlet and fluid outlet ports about midway along the second section, the fluid inlet and fluid outlet ports being located in the second section of the interior sidewall of the housing; at least two arcuate slots extending continuously into and through the rotor, wherein each of the slots is curved along a longitudinal slot axis; and at least two arcuate vanes, each of the vanes being shaped to be slidably seated in one of the slots, each of the vanes being movable in the corresponding slot between an extended position with the external edge of the vane adjacent the interior sidewall of the housing, and a retracted position wherein the external edge of the vane does not extend beyond the cylindrical surface of the rotor, each of the vanes being spaced from an adjacent vane about the rotor such that there is always at least one vane positioned between the fluid inlet and fluid outlet ports; wherein each of the vanes includes shoulder portions extending beyond the ends of the rotor; wherein the rotor disks include grooves aligned with the rotor slots and being configured for slidably receiving the shoulder portions of the vanes; and wherein low pressure of the fluid at the fluid inlet port assists each of the vanes to retract and high pressure of the fluid at the fluid outlet port assists each of the vanes to extend.
 2. The rotary pump according to claim 1, wherein each of the vanes includes an arcuate body portion conforming to the shape of the slot and a tip portion extending from the arcuate body portion.
 3. The rotary pump according to claim 2, wherein the tip portion is hingedly attached to the arcuate body portion to ride on the interior sidewall of the housing.
 4. The rotary pump according to claim 2, wherein the body of the rotor includes peripheral cutout portions shaped to receive the tip portions of the vanes when the vanes are in the retracted position.
 5. The rotary pump according to claim 2, wherein the tip portions include magnetic components and the rotor body includes magnetic components of similar polarity to repel the tip portion from the rotor body.
 6. The rotary pump according to claim 5, wherein the magnetic components of the rotor are located in the peripheral cutout portion.
 7. The rotary pump according to claim 2, wherein the tip portion has a triangular profile.
 8. The rotary pump according to claim 2, wherein the arcuate body portion includes an external hinge and the tip portion includes an arcuate surface and a flat surface.
 9. The rotary pump according to claim 2, wherein the tip portion includes magnetic components and the arcuate body portion includes magnetic components of similar polarity to repel the tip portion from the arcuate body portion.
 10. The rotary pump according to claim 1 further comprising a shock absorber placed in the grooves to prevent the vanes from impacting the ends of the grooves during the retraction of the vanes.
 11. The rotary pump according to claim 1, wherein the second section of the interior surface includes an outlet section that causes the vane to retract.
 12. The rotary pump according to claim 1, wherein the arcuate slots are diametrically opposed such that a distal vane end of the first arcuate slot is opposite on the rotor to a distal vane end of the second arcuate slot.
 13. The rotary pump according to claim 1, wherein the arcuate slots do not pass through the centre of axis of rotation of the rotor.
 14. The rotary pump according to claim 1, wherein the housing and the vanes are constructed so that, during operation of the rotary piston, fluid entering the housing through the inlet port is carried by the rotor, in each of compartments formed between adjacent vanes, the rotor surface between the vanes and the corresponding sections of the end walls and interior sidewall of the housing, until the adjacent vanes encompass the outlet port whereby the fluid is allowed to leave the housing.
 15. A rotary pump comprising: a shaft to rotate about a longitudinal axis; a rotor centrally secured to the shaft, the rotor having a body with spaced ends and a cylindrical surface extending between the spaced ends; a housing encasing the shaft and the rotor within an internal cavity, the housing having interior end walls and an interior sidewall, with fluid inlet and fluid outlet ports in the interior sidewall, a first section of the interior sidewall of the housing being cylindrical and curved with a constant radius over an angle of about approximately 180°, the first section being spaced a constant distance from confronting sections of the cylindrical surface of the rotor, and a second section of the interior sidewall of the housing extending between the extremities of the first section of the interior sidewall, the cylindrical surface of the rotor being proximal to the interior sidewall of the housing between the fluid inlet and fluid outlet ports about midway along the second section, the fluid inlet and fluid outlet ports being located in the second section of the interior sidewall of the housing; at least two arcuate slots extending continuously into and through the rotor, wherein each of the slots is curved along a longitudinal slot axis; and at least two arcuate vanes, each of the vanes being shaped to be slidably seated in one of the slots, each of the vanes being movable in the corresponding slot between an extended position with the external edge of the vane adjacent the interior sidewall of the housing, and a retracted position wherein the external edge of the vane does not extend beyond the cylindrical surface of the rotor, each of the vanes being spaced from an adjacent vane about the rotor such that there is always at least one vane positioned between the fluid inlet and fluid outlet ports; wherein low pressure of the fluid at the fluid inlet port assists each of the vanes to retract and high pressure of the fluid at the fluid outlet port assists each of the vanes to extend.
 16. A rotor for a pump, the rotor comprising: a rotor body with spaced ends and a rotor surface extending between the spaced ends; an arcuate slot extending continuously into and through the rotor body, wherein the slot is curved along a longitudinal slot axis; and an arcuate vane being shaped to be slidably seated in the slot, the vane being movable in the slot between an extended position with an external edge of the vane adjacent the interior sidewall of a housing, and a retracted position wherein the external edge of the vane does not extend beyond the rotor surface of the rotor body.
 17. The rotor of claim 16, wherein the rotor body includes two arcuate slots and the rotor includes two arcuate vanes.
 18. The rotor of claim 16 wherein the arcuate slot is curved along a longitudinal slot axis that is parallel with a rotator rotation axis of the rotor.
 19. The rotor of claim 16 wherein the vane is fluidly sealed in the arcuate slot such that fluid is inhibited from passing through or around the vane in the arcuate slot.
 20. The rotor of claim 16, wherein the arcuate vane includes an arcuate body portion conforming to the shape of the slot and a tip portion extending from the arcuate body portion. 